Communication control method in mobile communication system and base station used therefor

ABSTRACT

In the case where a PDSCH is transmitted by only one specific base station and a DPCH is simultaneously transmitted by a plurality of base stations while controlling a transmitting power of the PDSCH according to the DPCH, an optimum value of a power ratio between the PDSCH and the DPCH according to a position of a mobile station is optimized, and the receiving quality of the PDSCH at a fixed level regardless of the position of the mobile station on the soft handover is maintained to be constant. In a specific base station, a value of a ratio between the transmitting power of the PDSCH and that of the DPCH that is a dedicated channel is controlled to be optimized according to the position of the mobile station on the soft handover so that it becomes the ratio determined based on a measured value of a received power of a shared channel or the dedicated channel of a soft handover base station in the mobile station. To be more specific, the mobile station notifies the specific base station of these measuring results, and the specific base station notified thereof multiplies by a coefficient determined based thereon the transmitting power of the DPCH that is the dedicated channel transmitted by the base station itself and transmits it.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication control method in amobile communication system and a base station and a program recordmedium used therefor, and in particular, to the communication controlmethod of a channel from the base station to a mobile station on softhandover in a CDMA (Code Portion Multiple Access) cellular mobile radiocommunication system.

2. Description of the Prior Art

One of the cellular mobile communication systems is an HSDPA (High SpeedDownlink Packet Access) mode, which is a technology for transmittingpacketed data by using a high-speed downlink shared channel(downlink-specific) called HS-PDSCH (High Speed-Physical Downlink SharedChannel) in the case of transmitting to a mobile station large amountsof data (such as the data of a static image and a dynamic image) from acommunication network via a base station. It is a mode wherein, in thecase where the large amounts of data must be simultaneously transmittedto a plurality of mobile stations, this high-speed downlink sharedchannel called HS-PDSCH is shared time-wise (time sharing) to use thisone high-speed channel by sharing.

When the mobile station approaches a boundary of a cell in such acellular mobile communication system in the HSDPA mode, the mobilestation is in a state capable of communication by setting up channelswith a plurality of base stations having the cells near this boundary astheir service areas, which is called a soft handover state. At the timeof this soft handover, for example, channels are connected between acertain mobile station (MS) 10 and two base stations (BS) 1 and 2 asshown in FIG. 1.

As for these channels, there are two types as shown in FIG. 1, where onetype is a downlink-specific common pilot channel called CPICH (CommonPilot Channel), indicated as a CPICH 1 and a CPICH 2 corresponding tothe base stations 1 and 2 respectively. In addition, the other type is adedicated (physical) channel for uplink/downlink called DPCH (DedicatedPhysical Channel) and includes various communication data such ascontrol information and voice. It is also indicated as a DPCH 1 and aDPCH 2 corresponding to the base stations 1 and 2 in FIG. 1. Moreover,in FIG. 1, a PDSCH is the above-mentioned large-capacity data channel,which is a downlink-specific shared data channel.

Moreover, definitions of such various channels are disclosed in the 3GPP(3rd Generation Partnership Project) Specifications TS25.211V3.0.0(1999-10).

It adopts a method wherein, on the soft handover, a plurality of basestations 1 and 2 simultaneously transmit the DPCH to a mobile station10, and the PDSCH that is the data channel is transmitted by just onebase station (only the base stations 1 in FIG. 1) so as to controltransmitting power of this PDSCH in accordance with the DPCH, which isdisclosed in the 3GPP Report TR25.841V4.0.0 (2000-12).

According to this report, transmitting power P_(PDSCH) from the basestation of the PDSCH is determined as follows.

P _(PDSCH) =P _(DPCH1) ·A·C  (1)

Here, the transmitting power of the DPCH1 is P_(DPCH1), and A is aconstant and selected as A=1 for instance. And C is defined as follows.

P_(CPICH1)>P_(CPICH2)

In this case, C=C_(primary) (=2 to 3 dB), and if

P_(CPICH1)<P_(CPICH2,)

it is C=C_(non-primary) (=4 to 6 dB). In addition, P_(CPICH 1) andP_(CPICH 2) are the received power of the CPICH 1 and CPICH 2 in themobile station.

In another mobile communication system for performing data communicationfrom the base station to the mobile station by using the PDSCH, thetransmitting power of this PDSCH is not controlled but is fixed, andinstead, it is possible to select a plurality of transmission modes ofdifferent modulating methods or encoding methods. As for the modulatingmethods, there are QPSK (Quadrature Phase Shift Keying) capable oftransmitting 2 bits (4 values) by 1 symbol, 16 QAM (16 QuadratureAmplitude Modulation) capable of transmitting 4 bits (16 values) by 1symbol, 64 QAM (64 Quadrature Amplitude Modulation) capable oftransmitting 6 bits (64 values) by 1 symbol and soon. In addition, asfor the encoding methods, there are convolutional encoding of anencoding ratio ½ for performing encoding by 2 bits per information bit,the convolutional encoding of an encoding ratio ½ for performingencoding by 3 bits per information bit and so on.

FIG. 11 shows an example of selection of the transmission modes ofdifferent modulating methods. In FIG. 11, for instance, the transmissionmode is selected so that, a distant from a base station 51 to a mobilestation 52 is shorter, a transmitting speed becomes to be faster. To bemore specific, the base station 51 selects the transmission modes of 64QAM, 16 QAM and QPSK in increasing order of distance to the mobilestation 52.

While the DPCH is used together with the PDSCH in order to transmit andreceive control information on the data transmission by the PDSCH, thereis a method in the past, as that of selecting the above-mentionedtransmission modes of 64 QAM, 16 QAM and QPSK, wherein a range of thetransmitting power in the base station of the DPCH of the downlink isdetermined in advance so as to select the transmission mode according tothat transmitting power.

In this case, the mobile station measures receiving quality of the DPCHfrom the base station, compares the measured value to a reference value,and notifies the base station of increase or decrease in thetransmitting power of the DPCH so that the measured value becomes closeto the reference value. The base station increases or decreases thetransmitting power of the DPCH according to that notification, and alsoselects the transmission mode according to the transmitting power set upby the increase or decrease. For instance, as shown in FIG. 12, itselects the transmission modes of the 64 QAM, 16 QAM and QPSK inincreasing order of the transmitting power to be set up.

As for the method of determining the transmitting power of the PDSCHshown in the above-mentioned equation (1), it is a two-step controlmethod wherein the transmitting power of the PDSCH is determined byrendering the C of the equation (1) as C_(primary) if, of a plurality ofbase stations in the soft handover state, the base station setting upthe PDSCH is one having higher received power of the CPICH in the mobilestation (Primary), and by rendering the C as C_(non-primary) otherwise,resulting in a problem that continuous and elaborate control cannot beexerted. To be more specific, there is a fault that it is not possibleto maintain the receiving quality of the PDSCH at a fixed levelregardless of a position of the mobile station 10 on the soft handover.

SUMMARY OF THE INVENTION

An object of the present invention is to provide the communicationcontrol method in the mobile communication system and the base stationand a record medium used therefor, wherein, in the case where the PDSCHis transmitted by one specific base station and the DPCH issimultaneously transmitted by the plurality of base stations whilecontrolling the transmitting power of the PDSCH according to the DPCH,an optimum value of a power ratio between the PDSCH and the DPCH isoptimized according to the position of the mobile station, and thus itis possible to maintain the receiving quality of the PDSCH at a fixedlevel regardless of the position of the mobile station on the softhandover.

In addition, as for the above-mentioned method of selecting thetransmission mode, the PDSCH that is the data channel is transmitted byjust one base station, while the transmitting power of the DPCH in thebase stations is controlled, on the soft handover when the plurality ofbase stations simultaneously transmit the DPCH to the mobile station, bythe receiving quality generated by synthesizing the received DPCHtransmitted from the plurality of base stations in the mobile station,resulting in a value different from the transmitting power in the casewhere only one base station transmits the DPCH, so that there is a faultthat it is not possible to adequately select the transmission mode ofthe PDSCH and maintain the receiving quality of the PDSCH at a fixedlevel.

Another object of the present invention is to provide the communicationcontrol method in the mobile communication system and the base stationand the program record medium used therefor, wherein, in the case wherethe PDSCH is transmitted by one specific base station and the DPCH issimultaneously transmitted by the plurality of base stations whilecontrolling the transmission mode of the PDSCH according to thetransmitting power of the DPCH, the transmission mode of the PDSCH iscontrolled according to the position of the mobile station, and thus itis possible to maintain the receiving quality of the PDSCH at a fixedlevel regardless of the position of the mobile station on the softhandover.

According to the present invention, it is possible to acquire acommunication control method in a mobile communication system wherein amobile station and a plurality of base stations in a soft handover statewith this mobile station setting up a dedicated channel to the abovedescribed mobile station and informing a common pilot channel areincluded, and only a specific base station of the plurality of basestations in the soft handover state has a shared channel with the abovedescribed mobile station set up, the above described methodcharacterized by, in the above described mobile station, measuringreceived power of the above described dedicated channel or common pilotchannel transmitted from each of the above described plurality of basestations and notifying the above described specific base station of thismeasuring results information, and in the above described specific basestation, controlling data transmission of the above described sharedchannel based on transmitting power of the above described dedicatedchannel and the above described measuring results information, the abovedescribed controlling performed according to a ratio between a sum ofthe above described received power and the received power from the abovedescribed specific base station.

According to the present invention, it is possible to acquire thecommunication control method in the mobile communication system whereinthe mobile station and the plurality of base stations in the softhandover state with this mobile station setting up the dedicated channelto the above described mobile station and informing the common pilotchannel are included, and only the specific base station of theplurality of base stations in the soft handover state has the sharedchannel with the above described mobile station set up, the abovedescribed method characterized by, in the above described mobilestation, measuring the received power of the above described dedicatedchannel or common pilot channel transmitted from each of the abovedescribed plurality of base stations and notifying the above describedspecific base station of this measuring results information, and in theabove described specific base station, performing the data transmissionof the above described shared channel by the power determined based onthe above described measuring results information and the transmittingpower of the above described dedicated channel, and the above describeddetermined power being a value according to the ratio between the sum ofthe above described received power and the received power from the abovedescribed specific base station.

According to the present invention, it is possible to acquire thecommunication control method in the mobile communication system whereinthe mobile station and the plurality of base stations in the softhandover state with this mobile station setting up the dedicated channelto the above described mobile station and informing the common pilotchannel are included, and only the specific base station of theplurality of base stations in the soft handover state has the sharedchannel with the above described mobile station set up, the abovedescribed method characterized by, in the above described mobilestation, measuring receiving SIR (Signal to Interference Ratio) of theabove described dedicated channel or the above described common pilotchannel transmitted from each of the above described plurality of basestations and notifying the above described specific base station of thismeasuring results information, and in the above described specific basestation, controlling the data transmission of the above described sharedchannel based on the transmitting power of the above described dedicatedchannel and the above described measuring results information, and thiscontrolling performed according to the ratio between the sum of theabove described receiving SIR and the receiving SIR from the abovedescribed specific base station.

According to the present invention, it is possible to acquire thecommunication control method in the mobile communication system whereinthe mobile station and the plurality of base stations in the softhandover state with this mobile station setting up the dedicated channelto the above described mobile station and informing the common pilotchannel are included, and only the specific base station of theplurality of base stations in the soft handover state has the sharedchannel with the above described mobile station set up, the abovedescribed method characterized by, in the above described mobilestation, measuring the receiving SIR (Signal to Interference Ratio) ofthe above described dedicated channel or the above described commonpilot channel transmitted from each of the above described plurality ofbase stations and notifying the above described specific base station ofthis measuring results information, and in the above described specificbase station, performing the data transmission of the above describedshared channel by the power determined based on the above describedmeasuring results information and the transmitting power of the abovedescribed dedicated channel, and the above described determined powerbeing the value according to the ratio between the sum of the abovedescribed receiving SIR and the receiving SIR from the above describedspecific base station.

According to the present invention, it is possible to acquire thespecific base station in the mobile communication system wherein themobile station and the plurality of base stations in the soft handoverstate with this mobile station setting up the dedicated channel to theabove described mobile station and informing the common pilot channelare included, and only the specific base station of the plurality ofbase stations in the soft handover state has the shared channel with theabove described mobile station set up, the above described specific basestation characterized by, in response to the notification of themeasuring results information in the above described mobile station onthe received power of the above described dedicated channel or the abovedescribed common pilot channel transmitted from each of the abovedescribed plurality of base stations, controlling the data transmissionof the above described shared channel based on the transmitting power ofthe above described dedicated channel and the above described measuringresults information, this controlling performed according to the ratiobetween the sum of the above described received power and the receivedpower from the above described specific base station.

According to the present invention, it is possible to acquire thespecific base station in the mobile communication system wherein themobile station and the plurality of base stations in the soft handoverstate with this mobile station setting up the dedicated channel to theabove described mobile station and informing the common pilot channelare included, and only the specific base station of the plurality ofbase stations in the soft handover state has the shared channel with theabove described mobile station set up, the above described specific basestation characterized by, in response to the notification of themeasuring results information in the above described mobile station onthe received power of the above described dedicated channel or the abovedescribed common pilot channel transmitted from each of the abovedescribed plurality of base stations, performing the data transmissionof the above described shared channel by the power determined based onthis measuring results information and the transmitting power of theabove described dedicated channel, and the above described determinedpower being the value according to the ratio between the sum of theabove described received power and the received power from the abovedescribed specific base station.

According to the present invention, it is possible to acquire thespecific base station in the mobile communication system wherein themobile station and the plurality of base stations in the soft handoverstate with this mobile station setting up the dedicated channel to theabove described mobile station and informing the common pilot channelare included, and only the specific base station of the plurality ofbase stations in the soft handover state has the shared channel with theabove described mobile station set up, the above described specific basestation characterized by, in response to the notification of themeasuring results information in the above described mobile station onthe receiving SIR (Signal to Interference Ratio) of the above describeddedicated channel or the above described common pilot channeltransmitted from each of the above described plurality of base stations,controlling the data transmission of the above described shared channelbased on the transmitting power of the above described dedicated channeland the above described measuring results information, and thiscontrolling performed according to the ratio between the sum of theabove described receiving SIR and the receiving SIR from the abovedescribed specific base station.

According to the present invention, it is possible to acquire thespecific base station in the mobile communication system wherein themobile station and the plurality of base stations in the soft handoverstate with this mobile station setting up the dedicated channel to theabove described mobile station and informing the common pilot channelare included, and only the specific base station of the plurality ofbase stations in the soft hand over state has the shared channel withthe above described mobile station set up, the above described specificbase station characterized by, in response to the notification of themeasuring results information in the above described mobile station onthe receiving SIR (Signal to Interference Ratio) of the above describeddedicated channel or the above described common pilot channeltransmitted from each of the above described plurality of base stations,performing the data transmission of the above described shared channelby the power determined based on this measuring results information andthe transmitting power of the above described dedicated channel, and theabove described determined power being the value according to the ratiobetween the sum of the above described receiving SIR and the receivingSIR from the above described specific base station.

According to the present invention, it is possible to acquire a recordmedium having recorded a control program of the specific base station inthe mobile communication system wherein the mobile station and theplurality of base stations in the soft handover state with this mobilestation setting up the dedicated channel to the above described mobilestation and informing the common pilot channel are included, and onlythe specific base station of the plurality of base stations in the softhandover state has the shared channel with the above described mobilestation set up, the above described program characterized by, includinga process of, in response to the notification of the measuring resultsinformation in the above described mobile station on the received powerof the above described dedicated channel or the above described commonpilot channel transmitted from each of the above described plurality ofbase stations, controlling the data transmission of the above describedshared channel based on the transmitting power of the above describeddedicated channel and the above described measuring results information,the above described controlling performed according to the ratio betweenthe sum of the above described received power and the received powerfrom the above described specific base station.

According to the present invention, it is possible to acquire the recordmedium having recorded the control program of the specific base stationin the mobile communication system wherein the mobile station and theplurality of base stations in the soft handover state with this mobilestation setting up the dedicated channel to the above described mobilestation and informing the common pilot channel are included, and onlythe specific base station of the plurality of base stations in the softhandover state has the shared channel with the above described mobilestation set up, the above described program characterized by, includingthe process of, in response to the notification of the measuring resultsinformation in the above described mobile station on the received powerof the above described dedicated channel or the above described commonpilot channel transmitted from each of the above described plurality ofbase stations, performing the data transmission of the above describedshared channel by the power determined based on this measuring resultsinformation and the transmitting power of the above described dedicatedchannel, and the above described determined power being the valueaccording to the ratio between the sum of the above described receivedpower and the received power from the above described specific basestation.

According to the present invention, it is possible to acquire the recordmedium having recorded the control program of the specific base stationin the mobile communication system wherein the mobile station and theplurality of base stations in the soft handover state with this mobilestation setting up the dedicated channel to the mobile station andinforming the common pilot channel are included, and only the specificbase station of the plurality of base stations in the soft handoverstate has the shared channel with the above described mobile station setup, the above described program characterized by, including the processof, in response to the notification of the measuring results informationin the above described mobile station on the receiving SIR (Signal toInterference Ratio) of the above described dedicated channel or theabove described common pilot channel transmitted from each of the abovedescribed plurality of base stations, performing the data transmissionof the above described shared channel by the power determined based onthis measuring results information and the transmitting power of theabove described dedicated channel, and the above described determinedpower being the value according to the ratio between the sum of theabove described receiving SIR and the receiving SIR from the abovedescribed specific base station.

According to the present invention, it is possible to acquire acommunication control method in the mobile communication system whereinthe mobile station and the plurality of base stations in the softhandover state with this mobile station setting up the dedicated channelto the above described mobile station and informing the common pilotchannel are included, and only the specific base station of theplurality of base stations in the soft handover state has the sharedchannel with the above described mobile station set up, the abovedescribed method characterized by: in the above described mobilestation, measuring the received power of the above described dedicatedchannel or common pilot channel transmitted from each of the abovedescribed plurality of base stations and notifying the above describedspecific base station of these measuring results information, and in theabove described specific base station, determining one of the pluralityof transmission modes of different modulation or encoding methods basedon the above described measuring results information and thetransmitting power of the above described dedicated channel, andperforming data transmission of the above described shared channel inthe determined transmission mode, and the above described transmissionmode determined based on the value according to the ratio between thesum of the above described received power and the received power fromthe above described specific base station.

According to the present invention, it is possible to acquire thecommunication control method in the mobile communication system whereinthe mobile station and the plurality of base stations in the softhandover state with this mobile station setting up the dedicated channelto the above described mobile station and informing the common pilotchannel are included, and only the specific base station of theplurality of base stations in the soft handover state has the sharedchannel with the above described mobile station set up, the abovedescribed method characterized by, in the above described mobilestation, measuring the receiving SIR (Signal to Interference Ratio) ofthe above described dedicated channel or the above described commonpilot channel transmitted from each of the above described plurality ofbase stations and notifying the above described specific base station ofthese measuring results information, and in the above described specificbase station, determining one of the plurality of transmission modes ofdifferent modulation or encoding methods based on the above describedmeasuring results information and the transmitting data of the abovedescribed shared channel in the determined transmission mode, andperforming the data transmission of the above described shared channelin the determined transmission mode, and the above describedtransmission mode determined based on the value according to the ratiobetween the sum of the above described receiving SIR and the receivingSIR from the above described specific base station.

According to the present invention, it is possible to acquire thespecific base station in the mobile communication system wherein themobile station and the plurality of base stations in the soft handoverstate with this mobile station setting up the dedicated channel to theabove described mobile station and informing the common pilot channelare included, and only the specific base station of the plurality ofbase stations in the soft handover state has the shared channel with theabove described mobile station set up, the above described stationcharacterized by: in response to the notification of the measuringresults information in the above described mobile station on thereceived power of the above described dedicated channel or the abovedescribed common pilot channel transmitted from each of the abovedescribed plurality of base stations, determining one of the pluralityof transmission modes of different modulation or encoding methods basedon this measuring results information and the transmitting power of theabove described dedicated channel, and performing the data transmissionof the above described shared channel in the determined transmissionmode, and the above described transmission mode determined based on thevalue according to the ratio between the sum of the above describedreceived power and the received power from the above described specificbase station.

According to the present invention, it is possible to acquire thespecific base station in the mobile communication system wherein themobile station and the plurality of base stations in the soft handoverstate with this mobile station setting up the dedicated channel to theabove described mobile station and informing the common pilot channelare included, and only the specific base station of the plurality ofbase stations in the soft handover state has the shared channel with theabove described mobile station set up, the above described stationcharacterized by, in response to the notification of the measuringresults information in the above described mobile station on thereceiving SIR (Signal to Interference Ratio) of the above describeddedicated channel or common pilot channel transmitted from each of theabove described plurality of base stations, determining one of theplurality of transmission modes of different modulation or encodingmethods based on this measuring results information and the transmittingpower of the above described dedicated channel, and performing the datatransmission of the above described shared channel in the determinedtransmission mode, and the above described transmission mode determinedbased on the value according to the ratio between the sum of the abovedescribed receiving SIR and the receiving SIR from the above describedspecific base station.

According to the present invention, it is possible to acquire the recordmedium having recorded the control program of the specific base stationin the mobile communication system wherein the mobile station and theplurality of base stations in the soft handover state with this mobilestation setting up the dedicated channel to the mobile station andinforming the common pilot channel are included, and only the specificbase station of the plurality of base stations in the soft handoverstate has the shared channel with the above described mobile station setup, the above described program characterized by, including the processof, in response to the notification of the measuring results informationin the above described mobile station on the received power of the abovedescribed dedicated channel or the above described common pilot channeltransmitted from each of the above described plurality of base stations,determining one of the plurality of transmission modes of differentmodulation or encoding methods based on this measuring resultsinformation and the transmitting power of the above described dedicatedchannel, and performing the data transmission of the above describedshared channel in the determined transmission mode, and the abovedescribed transmission mode determined based on the value according tothe ratio between the sum of the above described received power and thereceived power from the above described specific base station.

According to the present invention, it is possible to acquire the recordmedium having recorded the control program of the specific base stationin the mobile communication system wherein the mobile station and theplurality of base stations in the soft handover state with this mobilestation setting up the dedicated channel to the above described mobilestation and informing the common pilot channel are included, and onlythe specific base station of the plurality of base stations in the softhandover state has the shared channel with the above described mobilestation set up, the above described program characterized by: includingthe process of, in response to the notification of the measuring resultsinformation in the above described mobile station on the receiving SIRof the above described dedicated channel or common pilot channeltransmitted from each of the above described plurality of base stations,determining one of the plurality of transmission modes of differentmodulation or encoding methods based on this measuring resultsinformation and the transmitting power of the above described dedicatedchannel, and performing the data transmission of the above describedshared channel in the determined transmission mode, and the abovedescribed transmission mode determined based on the value according tothe ratio between the sum of the above described receiving SIR and thereceiving SIR from the above described specific base station.

In addition, the above described transmission mode may also bedetermined based on the value acquired by multiplying the transmittingpower of the above described dedicated channel by the ratio between thesum of the above described received power and the received power fromthe above described specific base station. Moreover, the above describedtransmission mode may also be determined based on the value acquired bymultiplying the transmitting power of the above described dedicatedchannel by the ratio between the sum of the above described receivingSIR and the receiving SIR from the above described specific base station

Workings of the present invention will be described. The mobile stationnotifies the specific base station (the base station for transmitting aPDSCH) of each of the above measuring results, and the specific basestation notified thereof multiplies the transmitting power of a DPCHthat is the dedicated channel transmitted by the base station by acoefficient determined based on these measuring results so as to controltransmission by using that multiplication value.

To mention it further, when the transmitting power of the dedicatedchannel is controlled so that receiving quality of the signal of thededicated channel transmitted from one base station becomes fixed, thattransmitting power reflects a propagation loss from the base station tothe mobile station and a link state of noise power and interference wavepower in the mobile station.

Accordingly, in the case of performing the data transmission by usingthe shared channel from that base station, it is possible to exertcontrol reflecting the link state by controlling the data transmissionaccording to the transmitting power thereof.

However, when the transmitting power of the dedicated channel iscontrolled by synthesizing the signals of the dedicated channelstransmitted from the plurality of base stations in the mobile stationperforming the soft handover so that the receiving quality of thesynthesized signals becomes fixed, that transmitting power does notcorrectly reflect the link state from the specific base station to themobile station for performing the data transmission using the sharedchannel. It is because the receiving quality of the synthesized signalalso depends on the signals from the base stations other than thespecific base station.

According to the method of the present invention, it is possible toexert control not only using the transmitting power of the dedicatedchannel, but also estimating a difference between the receiving qualityof the signal from the specific base station and that of the signalwherein the signals from the plurality of base stations including thespecific base station are synthesized and reflecting the link state fromthe specific base station to the mobile station by using the difference.

For that reason, even if the link state changes due to the position ofthe mobile station, it is possible to maintain the link quality of thedata transmission at a fixed level and improve efficiency of the datatransmission.

To be more specific, the mobile communication system for controlling thetransmitting power of the PDSCH controls the value of the ratio betweenthe transmitting power of the PDSCH and the transmitting power of theDPCH that is the dedicated channel so that it becomes the ratiodetermined based on the measured values (receiving quality) of thereceived power and the receiving SIR (Signal to Interference Ratio) ofthe common channel or the dedicated channel in the mobile station so asto be optimized according to the position of the mobile station on thesoft handover in the base station for transmitting the PDSCH that is alarge-capacity shared data transmission line.

In addition, the mobile communication system capable of selecting thetransmission mode of the PDSCH controls the transmission mode so thatthe transmitting power per information bit transmitted by the PDSCH isdetermined based on the measured values (receiving quality) of thereceived power and the receiving SIR (Signal to Interference Ratio) ofthe common channel or the dedicated channel in the mobile station so asto be optimized according to the position of the mobile station on thesoft handover in the base station for transmitting the PDSCH that is alarge-capacity shared data transmission line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an simplified system diagram to which an embodiment of thepresent invention is applied;

FIG. 2 is a block diagram showing the embodiment of a mobile station ofthe present invention;

FIG. 3 is a flowchart showing operation of the mobile station in FIG. 2;

FIG. 4 is a format diagram of a DPCH that is a dedicated channel;

FIG. 5 is a block diagram showing another embodiment of the mobilestation of the present invention;

FIG. 6 is a block diagram showing the embodiment of a base station ofthe present invention;

FIG. 7 is a flowchart representing the operation of the base station inFIG. 6;

FIG. 8 is a block diagram showing the embodiment of the base station inthe second embodiment of the present invention;

FIG. 9 is a flowchart representing the operation of the base station inFIG. 8;

FIG. 10 is a diagram showing an example of the operation of transmissionmode selection in the second embodiment;

FIG. 11 is a diagram showing a concept of the transmission modeselection in the conventional example; and

FIG. 12 is a diagram showing an conventional example of the operation ofthe transmission mode selection.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will be described hereafter.First, a description will be made as to the case where, in a cellularmobile communication system in an HSDPA mode as shown in FIG. 1, amobile station 10 is in a soft handover state with base stations 1 and2, and a PDSCH that is a large-capacity line is set up from the basestation 1 to the mobile station 10.

In the present invention, the A of the equation (1) is set as(P1+P2)/P1. Here, P1 and P2 represent received powers of CPICH 1 andCPICH 2 in the mobile station 10 respectively. Accordingly, atransmitting power of the PDSCH in the base station 1 in the presentinvention is as follows.

P _(PDSCH) =P _(DPCH1)·{(P 1+P 2)/P 1}·C  (2)

Moreover, the C in this case is a predetermined value.

The transmitting power of the PDSCH is determined by a relationsatisfying this equation (2) so that the receiving quality of the PDSCHin the mobile station 10 will be maintained at a fixed level regardlessof a position of the mobile station 10 on the soft handover. It will beproved hereafter.

Now, if a propagation loss from the base station 1 to the mobile station10 is L1, the propagation loss from the base station 2 to the mobilestation 10 is L2, and an interference wave (disturbing wave) is I, aratio between a signal transmitted from the base station 1 in therelation of the equation (2) and interference wave power is as followsin the mobile station 10. $\begin{matrix}{\frac{P_{PDSCH}}{L_{1} \cdot I} = {\frac{P_{DPCH1}}{L_{1} \cdot I} \cdot \frac{P_{1} + P_{2}}{P_{1}} \cdot C}} & (3)\end{matrix}$

In the equation (3), if P_(PDSCH)/L₁ is S_(PDSCH), and P_(DPCH1)/L₁, isS₁, it will be as follows. $\begin{matrix}{\frac{S_{PDSCH}}{I} = {\frac{S_{1}}{I} \cdot \frac{P_{1} + P_{2}}{P_{1}} \cdot C}} & (4)\end{matrix}$

Now, the transmitting powers of a DPCH 1 and a DPCH 2 in the basestations are controlled by a high-speed power control loop so that thereceiving quality of the signals after synthesis becomes fixed. To bemore specific, the mobile station synthesizes the signals of the DPCH 1and the DPCH 2 and compares the receiving quality of the synthesizedsignals to a fixed desired value, and according to the results thereof,it notifies the base station of a command for giving an instruction forincreasing or decreasing the transmitting powers, so that each basestation increases or decreases the transmitting power of the DPCH 1 andthe DPCH 2 according to the notification. Each base station rendersinitial values of the transmitting powers fixed, and increases ordecreases the transmitting powers according to the same command from themobile station, and so both the transmitting powers are balanced andaccordingly transmitting powers P_(d1) and P_(d2) are equal as follows.

P_(d1)=P_(d2)=P_(d)  (5)

In addition, transmitting powers P_(c1) and P_(c2) of the CPICH 1 andthe CPICH 2 are fixed, and a transmitting power ratio of CPICH/DPCH inthe base station 1 and 2 are mutually equal.

Accordingly, it is as follows.

P _(c1) /P _(d1) =P _(c2) /P _(d2)  (6)

And from the equation (5), it is as follows.

P _(c1) /P _(d) =P _(c2) /P _(d)  (7)

And so it is as follows.

P _(c1) =P _(c2)(P _(c))  (8)

Accordingly, the equation (4) can be rewritten as follows.$\begin{matrix}\begin{matrix}{\frac{S_{PDSCH}}{I} = {\frac{S_{1}}{I} \cdot \frac{\frac{P_{c}}{L_{1}} + \frac{P_{c}}{L_{2}}}{\frac{P_{C}}{L_{1}}} \cdot C}} \\{= {\frac{S_{1}}{I} \cdot \frac{\frac{1}{L_{1}} + \frac{1}{L_{2}}}{\frac{1}{L_{1}}} \cdot C}} \\{= {\frac{S_{1}}{I} \cdot \frac{\frac{P_{d}}{L_{1}} + \frac{P_{d}}{L_{2}}}{\frac{P_{d}}{L_{1}}} \cdot C}}\end{matrix} & (9)\end{matrix}$

Furthermore, if the equation (9) is rewritten by using the equation (5),the following can be acquired. $\begin{matrix}\begin{matrix}{\frac{S_{PDSCH}}{I} = {\frac{S_{1}}{I} \cdot \frac{\frac{P_{d1}}{L_{1}} + \frac{P_{d2}}{L_{2}}}{\frac{P_{d1}}{L_{1}}} \cdot C}} \\{= {\frac{S_{1}}{I} \cdot \frac{S_{1} + S_{2}}{S_{1}} \cdot C}} \\{= {\frac{S_{1}}{I} \cdot \frac{\frac{S_{1}}{I} + \frac{S_{2}}{I}}{\frac{S_{1}}{I}} \cdot C}} \\{= {\left( {\frac{S_{1}}{I} + \frac{S_{2}}{I}} \right) \cdot C}}\end{matrix} & (10)\end{matrix}$

The inside of the parenthesis on the right side of the equation (10) isa sum of signal to interference ratios of receiving signals of the DPCH1 and the DPCH 2, representing the signal to interference ratio of thesignals after synthesizing the receiving signals at a maximum ratio,that is, the receiving quality of the synthesized signals, which is keptfixed by the high-speed power control loop so that, as revealed, thereceiving quality of the PDSCH in the mobile station shown in theequation (3) consequently becomes fixed.

Accordingly, the received powers P1 and P2 of the CPICH 1 and the CPICH2 of the base station 1 and 2 in the soft handover relation should bemeasured in the mobile station 10 with the measuring results notified tothe base station 1, where the P1 and P2 should be used to calculate thetransmitting power of the PDSCH from the equation (2) so as to transmitdata to the large-capacity line.

While the received powers of the CPICH 1 and the CPICH 2 are measured inthe mobile station 10 in the above example, it is also feasible tomeasure the received powers of individual pilot signals of the DPCH 1and the DPCH 2 instead and use them as the above P1 and P2. In thiscase, the equation in the second line of the equation (10) isimmediately acquired from the equation (4) and the equation in the lastline of the equation (10) also follows, so that the effect exactly thesame as using the received power of the CPICH can be obtained.

Moreover, while the condition shown in the equation (5), that is, thecondition that the transmitting powers P_(d1) and P_(d2) of the DPCH 1and the DPCH 2 are equal is required in the case of using the receivedpowers of the CPICH, the equation (10) holds without the above conditionin the case of using the DPCH.

While the mobile station 10 notifies the base station 1 of the receivedpower measured values P1 and P2, it may also notify P2/P1, P1/P2,(P1+P2)/P1, P1/(P1+P2) and so on or an average thereof in a section of apredetermined number of frames. Furthermore, it is also feasible toreceive the P1 and P2 on the base station side to calculate and averagethe above values.

Furthermore, it is also possible to use the value of A by raising it tothe αth power, in which case it is equivalent to multiplying a decibelvalue by an integer. In addition, it is also possible to set upper andlower limits to the A.

FIG. 2 is a block diagram of the embodiment of the mobile station of thepresent invention, and FIG. 3 is a simplified operation flowchartthereof. A received wave from an antenna 11 is supplied to a receptionportion 13 via a duplexer (DUP) 12 and is demodulated. The demodulationoutput is separated into user information and control information by achannel separation portion 14. Among the control information, commonpilot channels CPICHs are detected by detection portions 15 and 16respectively, and the received powers P1 and P2 are measured in powermeasurement portions 17 and 18 (step S1).

These measured values P1 and P2 are supplied to a notifying informationgeneration portion 19, where notifying information to the base station 1is generated (step S2).

This notifying information generation portion 19 generates any one ofthe ratio between the sum of the received powers of the signals from theplurality of base stations 1 and 2 and the received power of the signalsfrom a specific base station, the ratio between the sum of the receivedpowers of the signals from the plurality of base stations except thespecific base station and the received power of the signals from thespecific base station, and inverse numbers of these ratios. To be morespecific, it generates P1/P2, P2/P1, (P1+P2)/P1, P1/(P1+P2) or theaverage values of these several frames as the notifying informationbased on the measured values P1 and P2. This notifying information issynthesized with transmitting information in a synthesis portion 20, andis applied to a transmission portion 21 to be modulated so that it istransmitted to the base station 1 via the DUP 12 (step S3).

The notifying information at this time is transmitted by using an uplinkof the DPCH 1. FIG. 4 shows a format of the DPCH, where the uplink anddownlink are different. The uplink DPCH is comprised of a DPCCH(Dedicated Physical Control Channel) and a DPDCH (Dedicated PhysicalData Channel), and they are orthogonally modulated mutually. The DPCCHhas pilot signals (dedicated), transmission power control information(TPC), feedback information (FBI) and communication data. While this FBIincludes a CW (code word: specifying a primary base station) used forSSDT (site selection diversity transmission: a mode wherein only thebase station having the highest (primary) received power of the CPICH inthe mobile station performs data transmission), the system of thepresent invention does not adopt the SSDT mode so that this CW portionmay be used for the above-mentioned notifying information. In addition,it is a matter of course that another available bit may be used.

FIG. 5 is a block diagram of another embodiment of the mobile station ofthe present invention, and the portions equal to those in FIG. 2 areindicated by the same symbols. In this example, the DPCH is measuredinstead of the CPICH, and so the only difference is that the portions 15and 16 for measuring the CPICH in FIG. 2 are the portions 22 and 23 formeasuring the DPCH.

FIG. 6 is a block diagram of the embodiment of the base station of thepresent invention, and FIG. 7 is a rough operation flowchart thereof.The received wave from an antenna 31 is inputted to a reception portion33 via a DUP 32 and is demodulated. As for demodulation output, the DPCHis detected in a DPCH detection portion 34, and the notifyinginformation from the mobile station included therein is detected by anotifying information detection portion 35 (step S11).

This notifying information is inputted to a transmitting powerdetermination portion 36 and controls gain of a transmission amplifier37 so that the transmitting power of the PDSCH becomes the equation (2).To be more specific, a multiplication coefficient (P1+P2)/P1 for thetransmitting power of the DPCH not shown is generated, and control isperformed by multiplying the transmitting power of the DPCH by thiscoefficient (step S12), and it is modulated by a transmission portion 38so that the PDSCH is transmitted to the mobile station (step S13).Moreover, the CPICH and the DPCH are omitted in FIG. 6.

While a control amount of the transmitting power is determined by usingthe received powers of the CPICH and the DPCH in the mobile station inthe above-mentioned embodiment, it can be implemented just in the sameway by using a SIR (Signal to Interference Ratio) of the CPICH and theDPCH.

In addition, while a description was made as to the case where thenumber of the base stations on the soft handover is two, it applieslikewise to the cases where it is three or more, in which cases thevalue (coefficient) of the A in the equation (2) is (P1+P2+P3+ . . .)/P1.

It is evident that the flow in FIG. 7 for controlling operation of thebase station can be implemented by recording a program on a recordmedium and reading it to control the operation of hardware (a computer).

In the above embodiment, while an example of controlling thetransmitting power is shown as a method of controlling the datatransmission by using a shared channel, there is also the method ofcontrolling the data transmission wherein a modulation method or anencoding method is changed according to a link state while maintaining afixed transmitting power, and the present invention is also applicableto such control.

Furthermore, another embodiment (a second embodiment) of the presentinvention will be described. As in the embodiment described earlier, adescription will be made as to the case where, in the cellular mobilecommunication system in the HSDPA mode as shown in FIG. 1, the mobilestation 10 is in the soft handover state with base stations 1 and 2, andthe PDSCH that is the large-capacity line is set up from the basestation 1 to the mobile station 10. The base station 1 transmits theCPICH 1 and the PDSCH, and transmits and receives the DPCH 1 to and fromthe mobile station 10, and the base station 2 transmits the CPICH 2, andtransmits and receives the DPCH 2 to and from the mobile station 10. Inaddition, it is the same as the embodiment described earlier in that themobile station 10 measures the received powers P1 and P2 of the CPICH 1and the CPICH 2 respectively and notifies the base stations of theinformation thereon, and in that the transmitting power of the downlinkDPCH is controlled by the command notified by the mobile station forgiving the instruction for increasing or decreasing the transmittingpower.

In the mobile communication system of the second embodiment, it ispossible to select a plurality of transmission modes using modulationmethods such as QPSK (Quadrature Phase Shift Keying) capable oftransmitting 2 bits (4 values) by 1 symbol, 16 QAM (16 QuadratureAmplitude Modulation) capable of transmitting 4 bits (16 values) by 1symbol, 64 QAM (64 Quadrature Amplitude Modulation) capable oftransmitting 6 bits (64 values) by 1 symbol and so on. The number ofsymbols to be transmitted per second is fixed regardless of thetransmission mode. A determination of switching the above transmissionmodes is made by the base station 1. While these transmission modes mayhave encoding rates with different encoding methods, it is fixed here asthe encoding rate of ⅓ for instance in order to simplify thedescription.

On determination of switching the above transmission modes, the basestation notifies the mobile station 2 by using the downlink (DL) DPCH(Dedicated Physical Channel), and switches the transmission modes inpredetermined timing after the notification thereof, and the mobilestation 2 switches the reception modes in the same timing to receive thePDSCH transmitted by the base station.

In the determination of the transmission mode, the base station selectsthe transmission mode using the modulation method according to largenessof the multiplication value calculated by multiplying the transmittingpower P_(DPCH1) by the coefficient A as shown in FIG. 10. Here, thecoefficient A is set as (P1+P2)/P1. This coefficient A is the same ascoefficient A in the preceding embodiment.

In FIG. 10, the larger each threshold is, the easier it becomes to usemulti-valued modulation such as 64 QAM resulting in a higher bit errorrate, so that the threshold of an upper limit of the multiplicationvalue using the 64 QAM, for instance, is set at the value wherein, whenthe multiplication value is equal to the threshold of the upper limit ofthe 64 QAM, the bit error rate nearly becomes the desired value at the64 QAM. In addition, the threshold of an upper limit of themultiplication value using the 16 QAM is also set likewise at the valuewherein the bit error rate nearly becomes the desired value for the 16QAM when the multiplication value is equal to the threshold of the upperlimit of the 16 QAM. Moreover, it is relatively easy to determine thethresholds by performing it on condition of A=1 without performing thesoft handover since it is not necessary to calculate the value of the A.

Thus, transmission mode power of the PDSCH is determined by thelargeness of the multiplication value so that the receiving quality ofthe PDSCH in the mobile station 10 is maintained nearly at a fixed levelregardless of the position of the mobile station 10 on the softhandover. The reason for this will be described hereafter.

In general, it is possible to render the error rate of an informationbit as the desired value by maintaining the ratio between a receivedpower per information bit Eb and a noise power including an interferencepower No (Eb/No) nearly at a predetermined value. As this embodiment hasthe encoding rate of the transmission modes fixed, and it also has thetransmitting power fixed, that is the transmitting power per symbolfixed, the received power per bit at the 16 QAM of 4 bits by 1 symbol is½, and the received power per bit at the 64 QAM of 6 bits by 1 symbol is⅓ if a propagation path is fixed, compared with the case of selectingthe QPSK of 2 bits by 1 symbol.

Accordingly, if the propagation path is fixed, the Eb/No per bit is ½ atthe 16 QAM and it is ⅓ at the 64 QAM compared with the case of selectingthe QPSK.

Here, the case where only one base station is transmitting the DPCH tothe mobile station is considered first. The transmitting power of thedownlink DPCH is controlled so that the receiving quality of the DPCH inthe mobile station becomes fixed. In addition, the propagation paths ofthe DPCH and the PDSCH are the same. For this reason, when the state ofthe propagation path of the PDSCH changes and the transmitting power ofthe DPCH becomes ½ or ⅓ of the transmitting power of a certaincriterion, the Eb and No of the PDSCH becomes twice or three timesthereof respectively if the transmission mode remains fixed. Moreover,causes of this change of the condition of the propagation paths includedecrease in the propagation loss and the decrease in the noise powerincluding the interference power.

Accordingly, if the 16 QAM or the 64 QAM is selected as the transmittingpower of the DPCH becomes ½ and ⅓ when using the QPSK at thetransmitting power of a certain criterion, it results in increasing animprovement of the Eb/No due to the change by the number of bits persymbol even if the state of the propagation path changes, leading tomaintaining the Eb/No nearly at a fixed level with no increase thereinand also keeping the bit error rate nearly fixed.

Next, the case where the two base stations 1 and 2 are transmitting theDPCHs to the mobile station 10. The transmitting powers of the DPCH 1and the DPCH 2 are balanced, and these receiving signals are synthesizedat a maximum ratio in the mobile station. In addition, the transmittingpower ratio of the CPICH and the DPCH in the base stations 1 and 2 aremutually equal. At this time, if the transmitting power of the DPCH is ktimes as much as that of the CPICH, the received power of the DPCH 1 iskP1 and the received power of the DPCH 2 is kP2, and so the receivedpower of the DPCH 1 and the DPCH 2 after the synthesis is kP1+kP2.

Accordingly, even if the base station 2 transmits the DPCH 2 to themobile station, the received power becomes (P1+P2)/P1 times as much asthe received power kP1 in the case of only the DPCH 1 unless thetransmitting power of the DPCH 1 is changed. However, as thetransmitting power is controlled so that the receiving quality of theDPCHs after the synthesis becomes fixed, the transmitting powers of theDPCH 1 and the DPCH 2 become P1/(P1+P2) times as compared with the casewhere the DPCH 2 is not transmitted.

Accordingly, the transmitting power in the case where only one basestation transmits the DPCH is acquired by multiplying by (P1+P2)/P1 thetransmitting power in the case where two base stations transmit theDPCHs. In the present invention, this (P1+P2)/P1 is used as thecoefficient A to multiply the transmitting power of the DPCH thereby,and the transmission mode is determined based on that multiplicationvalue so that, even in the case of performing the soft handover, thetransmission mode not affected thereby, maintaining the Eb/No nearly atthe fixed level and keeping the bit error rate nearly fixed is selected.

Accordingly, in the mobile station 10, the received powers P1 and P2 ofthe CPICH 1 and the CPICH 2 of the base station 1 and 2 in the softhandover relation should be measured with the measuring results notifiedto the base station 1, where the P1 and P2 should be used to determinethe transmission mode of the PDSCH so as to transmit data to thelarge-capacity line.

While the mobile station 10 notifies the base station 1 of the receivedpower measured values P1 and P2, it may also notify P2/P1, P1/P2,(P1+P2)/P1, P1/(P1+P2) and so on or an average thereof in the section ofthe predetermined number of frames. Furthermore, it is also feasible toreceive the P1 and P2 on the base station side to calculate and averagethe above values. Furthermore, it is also possible to use the value of Aby raising it to the αth power, in which case it is equivalent tomultiplying the decibel value by the integer. In addition, it is alsopossible to set the upper and lower limits to the A.

While the mobile station requires a function of receiving the pluralityof transmission modes in a receiver thereof, it is the same as the firstembodiment otherwise and the method of transmitting the notifyinginformation from the mobile station to the base station is also thesame, and so the description thereof is omitted.

FIG. 8 is a block diagram of the embodiment of the base station of thepresent invention, and FIG. 9 is a rough operation flowchart thereof.The receiving signal from the antenna 31 is inputted to the receptionportion 33 via the duplexer DUP 32 and is demodulated. As for thedemodulation output, the DPCH is detected in the DPCH detection portion34, and the notifying information from the mobile station includedtherein is detected by the notifying information detection portion 35(step S21).

This notifying information is inputted to the transmitting powerdetermination portion 36, and the transmitting power of the downlinkDPCH is determined according to the command giving the instruction forincreasing or decreasing the transmitting power so as to control thegain of the transmission amplifier 37 by the determined transmittingpower (step S22). In addition, the determined transmitting power isinputted to a transmission mode determination portion 39, and on theother hand, the information on the received powers of the CPICH 1 andthe CPICH 2 in the mobile station 10 included in the notifyinginformation detected by the notifying information detection portion 35is also inputted to the transmission mode determination portion 39.

And the transmission mode determination portion 39 determines thetransmission mode of a transmission mode setting portion 40 based onsuch input information so that the Eb/No in the mobile station becomesnearly fixed. To be more specific, the multiplication coefficient A thatis (P1+P2)/P1 for the transmitting power of the DPCH is generated andcontrol is exerted to multiply the transmitting power of the DPCH bythis coefficient so that, as shown in FIG. 10, the transmission modecorresponding to the modulation method is determined according to thelargeness of that multiplication value (step S23), and the PDSCH ismodulated in the transmission mode determined by the transmissionportion 38 and transmitted to the mobile station, and the DPCH amplifiedby the transmission amplifier 37 is also transmitted to the mobilestation (step S24).

Moreover, in FIG. 8, reference numeral 41 denotes transmissioninformation, and the CPICH is omitted. In addition, it is evident herethat, instead of multiplying the transmitting power by the coefficient,the decibel values of the transmitting power and that of the coefficientmay be calculated to get the sum thereof.

While the transmission mode is determined by using the received powersof the CPICH and the DPCH in the mobile station in the embodimentdescribed above, it can be implemented just in the same way by using theSIR (Signal to Interference Ratio) of the CPICH and the DPCH. Inaddition, while a description was made as to the case where themodulation method is different according to the transmission mode, itcan also be implemented just in the same way in the case where theencoding method is different according to the transmission mode.

In addition, while a description was made as to the case where thenumber of the base stations on the soft handover is two, it also applieslikewise to the cases where it is three or more, in which cases thevalue (coefficient) of the A is (P1+P2+P3+ . . . )/P1.

It is evident that the flow in FIG. 9 for controlling the operation ofthe base station can be implemented by recording the program on therecord medium and reading it to control the operation of the hardware(computer).

As described above, according to the present invention, the receivedpowers and the receiving SIR of the CPICH and the DPCH from the basestation in the soft handover state with the mobile station are measuredon the soft handover, which are notified to the base station, and thenotified base station determines the transmitting power or thetransmission mode of the shared channel based on these measured values,so that it is possible to perform data transmission by the PDSCH of theconstantly fixed quality regardless of the position of the mobilestation, and so it has the effect of improving efficiency of the datatransmission.

What is claimed is:
 1. A communication control method in a mobile communication system wherein a mobile station and a plurality of base stations in a soft handover state with this mobile station setting up a dedicated channel to said mobile station and informing a common pilot channel are included, and only a specific base station of the plurality of base stations in the soft handover state has a shared channel with said mobile station set up, said method comprising: in said mobile station, measuring received power of said dedicated channel or common pilot channel transmitted from each of said plurality of base stations and notifying said specific base station of these measuring results; and in said specific base station, determining one of a plurality of transmission modes of different modulation or encoding methods based on said measuring results information and transmitting power of said dedicated channel, and performing data transmission of said shared channel in the determined transmission mode, said transmission mode being determined based on a value according to a ratio between a sum of said received power and the received power from said specific base station.
 2. A specific base station in a mobile communication system wherein a mobile station and a plurality of base stations in a soft handover state with this mobile station setting up a dedicated channel to said mobile station and informing a common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has a shared channel with said mobile station set up, wherein said specific base station, in response to notification of measuring results information in said mobile station on a received power of said dedicated channel or said common pilot channel transmitted from each of said plurality of base stations, determines one of a plurality of transmission modes of different modulation or encoding methods based on this measuring results information and transmitting power of said dedicated channel, and performs data transmission of said shared channel in the determined transmission mode, and said transmission mode is determined based on a value according to a ratio between a sum of said received power and the received power from said specific base station.
 3. A record medium having recorded a control program of a specific base station in a mobile communication system wherein a mobile station and a plurality of base stations in a soft handover state with this mobile station setting up a dedicated channel to the mobile station and informing a common pilot channel are included, and only a specific base station of the plurality of base stations in the soft handover state has a shared channel with said mobile station set up, said program including a process of: in response to notification of measuring results information in said mobile station on a received power of said dedicated channel or said common pilot channel transmitted from each of said plurality of base stations, determining one of a plurality of transmission modes of different modulation or encoding methods based on this measuring results information and transmitting power of said dedicated channel, and performing data transmission of said shared channel in the determined transmission mode, said transmission mode being determined based on a value according to a ratio between a sum of said received power and the received power from said specific base station. 